Technique for simultaneous acquisition of multiple independent MR imaging volumes with optimization of magnetic field homogeneity for spin preparation

Abstract

An MR imaging pulse sequence provides a method for simultaneous data acquisition from more than one independently prescribed volume while providing optimized field uniformity during both the magnetization preparation and data acquisition parts of the acquisition. The method is based on the use of a multi-element array coil where individual RF coil elements are more sensitive to one of the separate volumes of interest than to the other volumes. In the example of breast imaging, one scenario would have two coil elements that are designed to be most sensitive to the signal from the left breast, and two coil elements that are designed to be most sensitive to the signal from the right breast. An optimized pulse sequence and reconstruction technique is used to simultaneously acquire two separate sagittal imaging volumes corresponding to the left and right breasts with optimized fat suppression.

Description

BACKGROUND OF THE INVENTION[0001]This invention relates to magnetic resonance (MR) data acquisition. More particularly, it relates to methods for limiting the volume of interest and for simultaneously acquiring multiple imaging volumes during MR studies.[0002]An MR imaging system provides an image of a patient or other object in an imaging volume based on detected radio frequency (RF) signals from precessing nuclear magnetic moments. A main magnet produces a static magnetic field, or B0 field, over the imaging volume. Similarly, gradients coils within the MR imaging system are employed to quickly switch into effect magnetic radiance along mutually orthogonal x, y, z coordinates in the static B0 field during selected portions of an MR imaging data acquisition cycle. Meanwhile, an RF coil produces RF magnetic field pulses, referred to as a B1 field, perpendicular to the B0 field, within the imaging volume to excite the nuclei. The nuclei are thereby excited to precess about an axis at...

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Benefits of technology

[0007]The MR imaging pulse sequence described herein provides a method for simultaneous data acquisition from more than one independently prescribed volume while providing optimized field uniformity during both the magnetization preparation and data acquisition parts of the acquisition. For the acquisition of two volumes simultaneously, the invention may be used to either decrease scan time by as much as a factor of two compared to a sequential acquisition (while maintaining spatial resolution and signal-to-noise ratio or SNR). Alternatively, it can be used to increase spatial resolution by a factor of two with an approximate 10% increase in acquisition time as compared to a single-volume imaging procedure.

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Problems solved by technology

The first alternative results in different contrast characteristics for the volumes, and the possible loss of important early contrast uptake information for the volumes that are acquired later.

The second alternative compromises the spatial resolution of the study, and is an inefficient way to acquire data if the regions of interest are not close together.

Moreover, since it is often necessary to suppress the signal from fat to improve conspicuity of the areas of contrast agent uptake, the use of a larger volume usually results in compromised fat suppression due to the reduced efficacy of main field correction techniques for larger volumes.

Use of an axial or coronal volume to encompass both breasts compromises the spatial resolution of the image, and is inefficient because it requires the acquisition of data corresponding to the empty space between two breasts.

In addition, when imaging both breasts simultaneously with one large FOV, the main field homogeneity corrections applied (shim currents) are set to a single value for both volumes, a compromise that reduces the quality of fat suppression.

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